(a) Field of the Invention
The present invention relates to an apparatus and a method for unloading substrates. More specifically, the present invention relates to an apparatus and a method for unloading thin film transistor liquid crystal display (TFT-LCD) substrates having different sizes.
(b) Description of the Related Art
A TFT-LCD applies an electric field to liquid crystal material having anisotropic dielectricity and injected between two substrates. The intensity of the electric field controls the amounts of light that permeates through the substrates to obtain desired images.
One of the two substrates of the TFT-LCD is a TFT substrate on which a plurality of pixel electrodes and thin film transistors are formed. The other substrate is a color filter (CF) substrate on which red, green, and blue color filters, for displaying desired colors, and a black matrix are formed.
Today""s TFT-LCD manufacturing process forms a plurality of cells on a single master glass substrate. Each cell is cut to produce a TFT substrate or a CF substrate for a TFT-LCD. A plurality of cells on a master glass substrate enhance productivity. After forming a plurality of cells (e.g., 4, 6, or 8 cells) each of the master glass TFT substrate and the master glass CF substrate and after assembling them, they are then cut into individual pairs of TFT and CF substrates, thereby manufacturing a plurality of TFT-LCDs.
However, defects may occur in the cells of each master glass substrate in the above manufacturing process. When one of the two substrates of the resulting TFT-LCD is normal and the other defective, the entire resulting TFT-LCD becomes defective, and must be discarded.
Therefore, in the conventional manufacturing methods, master glass TFT and CF substrates are cut, for example, into one-half or one-third pieces, and the cut master glass TFT substrate and master glass CF substrate are assembled according to the cell defect pattern. The paired master glass substrates then proceed to the subsequent manufacturing process and produce a TFT-LCD comprised of either two normal or two defective TFT and CF substrates.
However, the conventional methods of unloading uncut master glass substrates and master glass substrates cut to xc2xd and ⅓ sizes to a cassette or the other process apparatus, cause problems since the substrates are unloaded without considering the various substrate size.
FIGS. 1(a) and (b) show a conventional method of unloading an uncut master substrate and a cut master substrate, respectively. Reference numeral 4 in FIG. 1(a) indicates the uncut master substrate and reference numeral 5 in FIG. 1(b) indicates the cut master substrate.
As shown in the drawings, the uncut master substrate 4 and the cut master substrate 5, on which predetermined processes have been performed in prior process apparatus, are placed on a handling station 1. At this time, the uncut master substrate 4 and the cut master substrate 5 are arranged at the front of the handling station 1. As shown in FIGS. 1(a) and (b), a conveying robot 2 lifts the uncut master substrate 4 and the cut master substrate 5 arranged at the front of the handling station 1, then moves them in the direction of the arrow to load on the cassette 3.
Such a conventional method moves the substrates 4 and 5 along a predetermined arc (based on inside edges of the substrates 4 and 5 closest to the conveying robot 2) without considering the size of the substrates 4 and 5. Therefore, although the uncut master substrate 4 is arranged to securely fit in the cassette 3, the cut master substrate 5 is loaded on the cassette 3 insecurely, because it is not placed adjacent to the closed side of the cassette 3. As a result, when transferring the cassette 3 loading the cut master substrate 5, vibrations or external shock can damage the substrate 5 because of the space between the outside edge of the substrate 5 and the closed side of the cassette 3. In other words, the substrate 5 can be damaged by moving toward the closed side of the cassette 3 and striking the walls.
It is an object of the present invention to provide an apparatus and method for unloading substrates that can place the substrates on a secure position of a cassette or a subsequent process apparatus by adjusting the position where the substrates are placed on a handling station or by adjusting a rotation radius of a conveying robot depending on a size of the substrates.
In order to achieve the object, the present invention provides an apparatus for unloading a substrate comprising a handling station arranging substrates having different sizes processed in prior process apparatus, a conveying robot lifting the substrate arranged on the handling station and loading the substrate to a predetermined position on a cassette or subsequent process apparatus regardless of a size of the substrate, and a process apparatus controller controlling the arrangement of the substrate on the handling station or the motions of the conveying robot in order to load the substrate on a predetermined position of the cassette or subsequent process apparatus regardless of the size of the substrate.
In order to load the substrates of different sizes on the predetermined secure position in a cassette or in a subsequent process apparatus, the system of the present invention either adjusts the length of the conveying robot""s sliding arm or repositions the substrates on the handling station depending on their sizes.
Methods for unloading substrates according to the present invention are also provided.